Construction of N = 2 Chiral Supergravity Compatible with the Reality Condition

We construct N = 2 chiral supergravity (SUGRA) which leads to Ashtekar's canonical formulation. The supersymmetry (SUSY) transformation parameters are not constrained at all and auxiliary fields are not required in contrast with the method of the two-form gravity. We also show that our formulation is compatible with the reality condition, and that its real section is reduced to the usual N = 2 SUGRA up to an imaginary boundary term.Comment: 16 pages, late

One-Dimensional Quantum Transport Affected by a Background Medium: Fluctuations versus Correlations

We analyze the spectral properties of a very general two-channel fermion-boson transport model in the insulating and metallic regimes, and the signatures of the metal-insulator quantum phase transition in between. To this end we determine the single particle spectral function related to angle-resolved photoemission spectroscopy, the momentum distribution function, the Drude weight and the optical response by means of a dynamical (pseudo-site) density-matrix renormalization group technique for the one-dimensional half-filled band case. We show how the interplay of correlations and fluctuations in the background medium controls the charge dynamics of the system, which is a fundamental problem in a great variety of advanced materials.Comment: 6 pages, 5 figures, final versio

The Orientation of the Frog's Egg

The classical experiments of Pflüger on the segmenting frog's egg, and the important conclusions drawn by Roux from a study of the same egg, have made it very desirable to have an accurate knowledge of the relation existing between the early segmenting egg and the position of the embryo with respect to the egg. Our work in relation to the orientation of the embryo has covered the ground somewhat more extensively than that of any previous author, since we have made use of the methods employed by all of them. Our results will be considered under three headings: 1st. Normal development and location of blastopore. 2nd. Results obtained by injury to definite portions of the early embryo. 3rd. Results obtained from embryos whose development had been modified by artificial means. A word of personal explanation ought to be added. The senior author is responsible for Sections I, II, IV, and V of the present paper. The work recorded in these was done in the spring of 1893. Section II is the record of the results obtained by Umè Tsuda while a student in the Biological Laboratory of Bryn Mawr College. This work was done during the winter of 1891-2 j the account written in the spring of 1892. Only very slight alterations have been made in this portion preparatory to publication

Electronic charges and electric potential at LaAlO3/SrTiO3 interfaces studied by core-level photoemission spectroscopy

We studied LaAlO3/SrTiO3 interfaces for varying LaAlO3 thickness by core-level photoemission spectroscopy. In Ti 2p spectra for conducting "n-type" interfaces, Ti3+ signals appeared, which were absent for insulating "p-type" interfaces. The Ti3+ signals increased with LaAlO3 thickness, but started well below the critical thickness of 4 unit cells for metallic transport. Core-level shifts with LaAlO3 thickness were much smaller than predicted by the polar catastrophe model. We attribute these observations to surface defects/adsorbates providing charges to the interface even below the critical thickness

Scaling Behavior in 4D Simplicial Quantum Gravity

Scaling relations in four-dimensional simplicial quantum gravity are proposed using the concept of the geodesic distance. Based on the analogy of a loop length distribution in the two-dimensional case, the scaling relations of the boundary volume distribution in four dimensions are discussed in three regions: the strong-coupling phase, the critical point and the weak-coupling phase. In each phase a different scaling behavior is found.Comment: 12 pages, latex, 10 postscript figures, uses psfig.sty and cite.st